This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have crystals of multiple integral membrane protein transporters and ligand-gated ion channel receptors that include the GltPh aspartate transporter, LeuT leucine transporter and two eukaryotic ligand-gated ion channels for which there is currently no high resolution structural data. We aim to carry out specific mechanistics studies on GltPh and LeuT and to perform MAD (SeMet) experiments on the two ligand-gated ion channel proteins in order to solve the phase problem.